Plastics container

ABSTRACT

A blow-molding method and its apparatus and a molded drum thereby are improved in that: a lower mold is divided into two pieces, i.e., a split-type mold having a ring-like configuration and a lower mold itself, so that the molding operation of a chime of the molded drum is facilitated.

This is a division, of application Ser. No. 783,591 filed Oct. 3, 1985.

BACKGROUND OF THE INVENTION

1. Field of the Invention:

The present invention relates to a hollow-molding method and a moldingapparatus for conducting the same method and a container manufactured bythe same method, and particularly to a plastics container provided witha projection generally called "chime" in its top portion, and a methodand an apparatus for molding the same container, which chime has apredetermined configuration with predetermined width and height.

2. Description of the Prior Art:

In the plastics container, particularly, in a large-size one a capacityof which is 50 to 200 1 in its volume, there is provided a projection,for example such as an angular flange having a predeterminedconfiguration with predetermined width and height in order to facilitateits handling and shipping, which projection is generally called "chime".It is generally preferable that the chime is wider in its width andhigher in its height.

Hitherto, in a conventional method for forming the chime, the chime ismanufactured according to the actuator process. However, in suchconventional method, the following problems exist: namely.

(I) it is difficult to obtain a good timing for moving a mold;

(II) restrictions on the width and the height of the chime exist;

(III) operation of the mold is complex; and

(IV) in case that a plastics having a good fluidity is employed, suchplastics is apt to drip in molding operation of a container so that abiased wall thickness is apt to be produced in such molded container.

Further, anoth conventional molding method and apparatus have beenproposed in Japanese Patent Laid-open No. 207101/1984 filed by theapplicant for the present application, which conventional apparatus isshown in FIG. 2, wherein: the reference numeral 1 designates a die forextruding molten resin; the numeral 2 designates a lower mold with aconcave portion 2a which has a predetermined configuration andpredetermined width and heigh; the numeral 3 designates a lift cylinderfor performing an up-and-down movement of the lower mold 2; the numeral4 designates an aie nozzle provided in the lift cylinder 3; the numerals5A and 5B designate a pair of opposite side molds; the numerals 6A and6B designate a pair of opposite cylinders for moving the opposite sidemolds 5A and 5B; the numeral 7 designates a hole for passing a heatedsteam or a cooling water; and the numeral 8 designates a cooling waterhole. All of the inner surfaces of the lower mold 2, and the oppositeside molds 5A and 5B and the lower surface of the die 1 are coated withfluorine contained resin. Incidentally, a notch portion 1a is formed ina peripheral portion of the the die 1, in which notch portion 1a thelower mold 2 is inserted. On the other hand, for facilitating anoperation of a drum handling machine in shipping, as shown in FIG. 5 thechime "A" is provided with a projecting portion A1 in its lower outerperiphery. Due to such provision of the projecting portion A1, anoutside ring portion of the concave portion 2a of the lower mold 2 isformed into a separate split mold, i.e., a chime ring B which isprovided with a notch portion B1 corresponding to the projecting portionA1, to make it possible that the chime ring B is separated from thechime when the molding operation of the product is completed.

On the other hand, in such apparatus, after the lower mold 2 is liftedso that the lower mold 2 is brought into a press contact with the die 1to form a top portion of the plastics container, the lower mold 2 islowered to perform a parting operation of the plastics product. At thistime, since the molten resin received in the chime A portion swellsagain so that the chime ring B is pushed up in the notch portion B1thereof, the chime ring B is lifted. Consequently, the top portion ofthe chime ring B projects upward beyond the predetermined level when thelower mold 2 is lowered to a predetermined position. As a result, at atime when the side molds 5A, 5B are closed, such side molds 5A, 5Binterferes with the chime ring B to jam the same while the projectingportion A1 varies in its width. Consequently, in the conventionalmolding apparatus, the parting operation of the lower mold 2 constitutesone step in the molding operation to extend a necessary molding time andto make it difficult to automate the molding operation.

Further, in the molding operation of the plastics container by means ofthe conventional blow-molding apparatus, there is a tendency to producea V-shaped notch N in its pinch-off portion as shown in FIG. 15D todecrease an impact strength of the molded product in drop and to make iteasy that the molded product is exfoliated. These are problems inherentin the conventional molding method and apparatus.

In order to resolve the above problems, it is possible to modify thepinch-off portion of the mold in its configuration and to modify themolding conditions, particularly to decrease a mold-clamping speed , sothat it is possible to improve the pinch-off portion to the extent of acondition shown in FIG. 15E. However, such improvement is notsufficient, while the decrease in the mold-clamping speed leads to apoor operativity. the inventor of the present invention has been foundthat a cooling speed of the parison in the prior art causes the aboveproblems, from various researches.

On the other hand, as the drum becomes larger in size, the drum becomesto be mechanically transferred, stacked and stored, by means of aspecial handling machine, for example such as the drum handling machine.Consequently, it is necessary to make it possible that the drum iseasily and surely clamped by the handling machine and detached easilyand surely therefrom. However, the drum molded by the conventionalmethod and apparatus has the following problems:

(1) it is difficult to glasp the chime of the drum by the handlingmachine;

(2) the ground plate of the drum is substantially in diameter similar tothe top portion of the same drum to make it difficult to stack the drumsinto neat piles;

(3) since in a falling down condition the drum contacts the ground inits whole trunk, it is difficult to change its rolling direction; and

(4) since the up and down sides of the drum are not changed, the bottomsurface of the ground plate is always subjected to a load, while sincethe pinch-off portion is formed in the bottom surface of the groundplate in a lateral straight line manner, the ground plate lacks inrigidity in the bottom surface thereof.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a method and anapparatus for molding a plastics container and the thus molded plasticscontainer, so that a chuck having a desired configuration is formed asit is designed with a simple mold operation control in the top portionof the container with the use of any resin.

According to a first aspect of the present invention, there is provideda method for molding a plastics container, in which method: there areprovided a lower mold provided with a concave portion for forming a topportion of the plastics container having a chime in its top portion,which concave portion has a predetermined configulation withpredetermined width and height; and a pair of opposite side molds formolding a side and bottom portions of the plastics container, whichlower mold is lifted toward a die by means of a lift cylinder to form apredetermined clearance between the die and itself so that apredetermined amount of a molten resin is extruded from the die, andthen the lower mold is further lifted by means of the lift cylinder tobe brought into a press contact with the die so that the top portion ofthe plastics container is molded, and therefore the molten resin isfurether extruded from the die at a predetermined parison speedaccording to which speed the lift cylinder is lowered to a predeterminedposition so that the lower mold is lowered to a predetermined positionin which position the opposite side molds are closed so that ablow-molding operation is conducted to mold the plastics containerprovided with the chime in its top portion.

According to a second aspect of the present invention, there is provideda method for molding a plastics container, in which method: there areprovided a lower mold provided with a concave portion for forming a topportion of the plastics container having a chime in its top portion,which concave portion has a predetermined configulation withpredetermined width and height; and a pair of opposite side molds formolding a side and bottom portions of the plastics container, whichlower mold is lifted toward a die by means of a lift cylinder to form apredetermined clearance between the die and itself so that apredetermined amount of a molten resin is extruded from the die, andthen the lower mold is further lifted by means of the lift cylinder tobe brought into a press contact with the die so that the top portion ofthe plastics container is molded, and thereafter the molten resin isfurther extruded from the die at a predetermined parison speed accordingto which speed the lower mold is further lowered to a further lowerposition than a predetermined position by means of the lift cylinder, inwhich further lower position the lower mold is temporarily held in astationary condition in which condition the side molds are closed, andthen the lower mold is lifted again by the lift cylinder to be broughtinto abutting contact with the side molds so that the lower mold ispositioned in a predetermined position where the blow-molding operationis conducted, whereby the plastics container provided with the chime inits top portion is molded.

According to a third aspect of the present invention, there is provideda blow-molding apparatus for a plastics container, in which apparatus:there are provided a lower mold provided with a concave portion forforming a top portion of the plastics container having a chime in itstop portion, which concave portion has a predetermined configurationwith predetermined width and height; and a pair of opposite side moldsfor molding a side and bottom portions of the plastics container, whichlower mold is lifted toward a die by means of a lift cylinder to form apredetermined clearance between the die and itself so that apredetermined amount of a molten resin is extruded from the die, andthen the lower mold is further lifted by means of the lift cylinder tobe brought into a press contact with the die so that the top portion ofthe plastics container is molded, and thereafter the molten resin isfurther extruded from the die at a predetermined parison speed accordingto which speed the lift cylinder is lowered to a predetermined positionso that the lower mold is lowered to a predetermined position where theopposite side molds are closed so that a blow-molding operation isconducted to mold the plastics container provided with the chime in itstop portion characterized in that:

an outside ring portion of the concave portion of the lower moldconstitutes a separate split mold between which split mold and the lowermold there is provided a connecting means for selectively connecting thesplit mold with the lower mold.

According to a fourth aspect of the present invention, there is provideda plastics container which is a plastics container molded by ablow-molding method and provided a chime in its top portion, whichplastics container is provided with: an annular projection formed in anouter periphery of the chime; suitable numer of ring-like bands formedin an outer periphery of a trunk portion of the plastics container, adiameter of each of which ring-like bands is similar to an outerdiameter of the annular projection; a ground plate which is formed intoa size adapted to an inner diameter of the chime in its bottom surfaceby virtue of its curved surface portion provided in an outer peripheryof the plastics container; and a cross-rib portion provided inside theground plate in projecting manner and having a pinch-off portion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 to 3 are views showing an embodiment of a molding method of aplastic container according to the present invention, wherein:

FIG. 1 shows a condition in which the lower mold is positioned near thethe die from which the molten resin is extruded;

FIG. 2 shows a condition in which the lower mold is brought into a presscontact with the die so that the top porportion of the plasticscontainer in which top portion the chime is provided is molded;

FIG. 3 shows a condition in which the lower mold is lowered;

FIG. 4 shows a condition in which the lower mold is lowered to apredetermined position while the opposite side molds are closed to makeit possible to conduct a blow-molding operation;

FIGS. 5 to 9 show a partial improvement of the above embodiment of themolding method of the plastics container according to the presentinvention. wherein:

FIG. 5 shows a condition in which the lower mold begins to be lowered;

FIG. 6 shows a condition in which the lower mold is temporarily held ina stationary condition after it is lowered;

FIG. 7 shows a condition in which the side molds are closed;

FIG. 8 shows a condition in which the lower mold is lifted again to bebrought into a press contact with the side molds;

FIG. 9 shows a condition in which the blow-molding operation iscompleted and the thus molded plastics container is ejected from thelower mold;

FIGS. 10 and 11 show longitudinal sectional views of the lower moldemployed in the molding apparatus of the present invention;

FIGS. 12 to 14 are explanatory view for showing the details of thepinch-off portion;

FIGS. 15A to 15C show sectional configurations of the pinch-off portion;

FIGS. 16A is a partially broken side view of the plastics containermolded according to the molding method of the present invention; and

FIG. 16B is a bottom view of the thus molded plastics container.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

According to a molding method of a plastics container of the presentinvention, a mold is divided into three pieces of: a lower mold formolding a top portion of the plastics container which top portion isprovided with a chime; a mold for molding a side portion of the plasticscontainer and a pair of side molds for molding a bottom portion of theplastics container, so that the top portion of the plastics containerwhich top portion is complex in its construction is firstly molded inthe lower mold to make it possible that a chime having a desiredconfiguration is easily molded as it is designed. Further, according tothe molding method of the present invention, a speed of a lift cylinderfor conducting an up-and-down movement of the lower mold is adjusted tomeet with a flow speed of a parison so that so-called dripping of theresin is prevented, and whereby it is possible to mold the plasticcontainer as it is designed with the use of any resin without producinga biased wall portion in the plastics container.

The molding method of the present invention will be described withreference to the drawings.

In FIGS. 1 to 4, wherein: the reference numeral 1 designates a die forextruding a molten resin; the numeral 2 designates a lower mold providedwith a concave portion 2a having a predetermined configuration andpredetermined width and height for molding a top portion of the plasticscontainer; the numeral 3 designates a lift cylinder for conducting anup-and-down movement of the lower mold 2; the numeral 4 designates anair nozzle provided in the lift cylinder 3; the numerals 5A and 5Bdesignate a pair of opposite side molds for molding a side portion and abottom portion of the plastics container; the numerals 6A and 6Bdesignate transfer cylinders for transferring the side molds 5A and 5B;the numeral 7 designates a hole for passing heated steam or coolingwater; and the numeral 8 designates a cooling water hole. All of theinner surfaces of the molds 2, 5A, 5B and the lower surface of the die 1are coated with fluorine contained resin. Incidentally, a notch portion1a is formed in a periphery of the die 1, in which notch portion 1a thelower mold 2 is inserted to make it possible to extrude the resinreceived in the central concave portion 2b of the lower mold 2 so that acavity is prevented from being produced in the molded plasticscontainer. Further, it is possible to control a wall thickness of theplastics container by adjusting a travelling distance of the lower mold2. However, it is also possible to extrude a larger amount of the resinthan a volume of the concave portion 2b without providing the notchportion 1a. Incidentally, it is also possible to provide a taper in aninner peripheral surface 2c of the concave portion 2a so that a draft isprovided between such inner peripheral surface 2c and the notch portion1a.

Now, the embodiment of the molding method of the plastics containerprovided with the chime in its top portion, in which method theabove-mentioned molds are employed, will be described.

According to the embodiment of the molding method of the presentinvention, the lower mold 2 is lifted toward the die 1 by means of thelift cylinder 3 to form a predetermined clearance between the die 1 andthe lower mold 2, which clearance is adjusted according to a necessaryamount of the resin to be molded. In this condition. the molten resin ismeasured by means of, for example such as a timer and extruded from thedie 1 as shown in FIG. 1.

Then, after such measurement of the molten resin, the lower mold 2 islifted again by means of the lift cylinder 3 to be brought into a presscontact with the die 1, whereby the top portion of the plasticscontainer, which top portion is provided with the chime, is molded asshown in FIG. 2.

Then, the molten resin received in an accumulator is extruded from thedie 1 by means of a ring piston, and at this time a small amount of airis injected from a pre-blow air nozzle 9 in order to prevent the parisonfrom being in a vacuum condition, while the lower mold 2 is lowered bythe lift cylinder 3 according to a parison speed so that a parison P isformed in expanded condition, which parison P is provided with a chime4a in its lower end as shown in FIG. 3. After the lower mold 2 islowered to a predetermined position, the opposite side molds 5A and 5Bare closed so that a pressurized air is injected from the nozzle 4 toconduct a blow-molding operation as shown in FIG. 4. In the blow-moldingoperation, the plastics container is molded in an inverted condition. Inuse, the plastics container is used in its normal condition. Therefore,according to the present invention, it is possible to obtain theplastics container "A" provided with a chime "a" in its top portion.

Although, in the above embodiment of the present invention, the numberof the nozzle 4 is only one, it is also possible to employ a pluralityof nozzles 4 as required.

As described above, according to the molding method of the plasticscontainer of the present invention, it is possible to mold the topportion of the plastics container, which top portion is provided withthe chime, as it is designed, and to prevent the dripping of the resinso that it is possible to mold the plastics container having a wallthickness as designed.

However, in this molding method, there is a problem in that it isdifficult to stop the lower mold 2 in a predetermined lowered positionshown in FIG. 3 in a precise manner due to an adjusting accuracy of alimit switch for controlling a position of the lift cylinder 3.

As a result, when the lower mold 2 is stopped in a position higher thana predetermined position, the side molds 4a, 4b interfere with the lowermold 2 to be jammed when they are closed. On the other hand, when thelower mold 2 is stopped in a position lower than a predeterminedposition, a clearance is produced between the side molds 4a, 4b and thelower mold 2 so that the blow-molding operation can not be conducted ina correct manner, whereby the molded product varies in its accuracy.Consequently, the above-mentioned problem makes it difficult to automatethe molding operation.

Further, in this molding method, there is another problem in that animpact strength of the molded container decreases because a local thinwall portion Q is produced in a portion of the parison P due to ashrinkage of the parison P, which shrinkage leads to a decrease of aweld strength of the parison P in its resin material. In order toresolve the above another problem, another molding method is proposedaccording to the present invention. According to this another moldingmethod, the lower mold is lifted to be brought into a press contact intothe die so that a top portion of the plastics container is formed, andthereafter a molten resin is extruded from the die while the lower moldis lowered by means of the lift cylinder to a position lower than apredetermined position, in which lower position the lower mold isstopped while the side molds are closed, and then the lower mold islifted again by means of a lift cylinder to be brought into a abuttingcontact with the side molds so that the lower mold is positioned in apredetermined position where the blow-molding operation is conducted, sothat the plastics container provided with the chime in its top portionis molded.

Consequently, it is possible to position the lower mold in apredetermined position according to the above another molding method, sothat the lower mold is easily brought into a press contact with the sidemolds, whereby a clearance between the side molds and the lower mold iseliminated. As a result, it is possible to prevent the side molds frombeing jammed with respect to the lower mold, and also possible toconduct the blow-molding operation in a correct manner to make itpossible to automate such blow-molding operation. Further, it is alsopossible to decrease the shrinkage of the parison so that the local thinwall portion is prevented from being produced in the top portion of theparison, whereby the weld strength of the parison in its material isincreased and in turn the impact strength of the thus molded containeris also increased.

It is preferable to set the lower position where the lower mold istemporarily stopped, in a position lower than the bottom portion of theside molds by a distance of 10 to 50 mm.

The above another molding method of the present invention will bedescribed hereinbelow with reference to the drawings.

In FIGS. 1 to 5, the reference numeral 2 designates a lower moldprovided with a concave portion 2a which has a predeterminedconfiguration and predetermined width and height for molding a topportion of a plastics container, which top portion is provided with achime c. However, in this embodiment, in contrast with the embodimentshown in FIGS. 1 to 4, an outer portion of the concave portion 2a of thelower mold 2 constitutes a separate split mold which is a chime ring 2bwhich is detachably attached to the lower mold 2 through a suitablemeans (not shown). The reference numeral 3 designates a lift cylinderfor conducting an up-and-down movement of the lower mold 2; the numeral5A and 5B designate a pair of opposite side molds for molding a sideportion and a bottom portion of the plastics container, in lowerportions of which side molds 5A and 5B there are provided notch portions5C. All of the inner surfaces of the lower mold 2 and the side molds 5A,5b are coated with fluorine contained resin.

After molding the top portion provided with the chime of the plasticscontainer according to the molding operation shown in FIGS. 1 and 2, amolten resin received in an accumulator is extruded from the die 1 bymeans of a ring piston, while a small amount of air is injected from apre-blow nozzle 9 in order to prevent the parison P form being in avacuum condition, and at this time, the lower mold 2 is lowered by thelift cylinder 3 at a speed similar to the parison speed as shown in FIG.5, so that the lower mold 2 is temporarily stopped in a positionslightly lower than the bottom portions of the side molds 5A, 5B, i.e.,lower than a lever of the notch portions 5C of the side molds 5A, 5B bya distance D of 10 to 50 mm, whereby the parison P provided with thechime C in its lower end is formed in an expanded condition as shown inFIG. 6.

Then, the side molds are closed as shown in FIG. 7. After the side molds5A, 5B are closed, the lower mold 2 is lifted again by the lift cylinder3 so that the chime ring 2b is brought into an abutting contact with thenotch portions 5C of the side molds 5A, 5B, whereby the clearancebetween the lower mold 2 and the side molds 5A, 5B is eliminated asshown in FIG. 8. In this condition, a pressurized air is injected intothe parison P from a nozzle (not shown) so that the blow-moldingoperation is performed. After the blow-molding operation is finished,the chime ring 2b is disconnected from the lower mold 2 so that thelower mold 2 is lowered by the lift cylinder 3, whereby the lower mold 2is separated from the molded container "A" as shown in FIG. 9. Finally,the side molds 5A, 5B are opened while the chime ring 2b is split to beseparated from the molded container "A", so that the plastics container"A" provided with the chime C in its top portion is obtained.

According to the molding method of the present invention as describedabove, it is possible to eliminate the clearance between the side molds5A, 5B and the lower lold 2 so that the side molds 5A, 5B are preventedfrom being jamed with respect to the lower mold 2 and the blow-operationof the pressurized air in the blow-molding operation is correctlyconducted, whereby it is possible to automate the molding method of thepresent inventio. Further, at this time, it is also possible todecdrease the shrinkage of the parison P so that it is possible toprevent the local thin wall portion from being produced in a parison'sportion corresponding to the top portion of the molded container,whereby the weld strength of the parison P in its material is increased,and in turn the impact strength of the molded container is alsoincreased.

In the above molding method of the present invention, it is possible toemploy the following molding apparatus, an embodiment of which apparatusis shown in FIGS. 1 to 9. Namely, in FIG. 1, the reference numeral 1designates a die; the numeral 2 designates a lower mold provided with aconcave portion 2a which has a predetermined configuration andpredetermined width and height for molding a top portion of the plasticscontainer, which top portion is provided with a chime; the numeral 3designates a lift cylinder for conducting an up-and-down movement of thelower mold 2; the numeral 4 designates an air nozzle provided in thelift cylinder 3; the numerals 5A, 5B designate a pair of opposite sidemolds for molding a side portion and a bottom portion of the plasticscontainer; the numerals 6A, 6B designate a pair of opposite transfercylinders for transferring the side molds 5A, 5B; the numeral 7designates a hole for passing a heated steam and a cooling water; thenumeral 8 designates a cooling water hole formed in the side molds 5A,5B; and all of the inner surfaces of the side molds 5A, 5B and a lowersurface of the die 1 are coated with fluorine contained resin.Incidentally, in a periphery of the die 1, there is formed a notchportion 1a in which the lower mold 2 is inserted.

On the other hand, in order to facilitate the use of the drum handlingmachine, i.e., a drum clipper in a handling operation of the drum, insome cases there is provided a projecting portion in an outer peripheryof an upper portion of the chime "A". In such cases, as shown in themolding method of FIGS. 5 to 9, an outer ring portion of the concaveportion 2a of the lower mold 2 constitutees a separate split mold, i.e.,a chime ring B which corresponds to the projecting portion of the cime"A" to make it possible that the chime ring B is split so as to beseparated from the chime "A" when the molding operation is finished.

However, the above molding apparatus of the present invention has thefollowing problem: namely, in this molding apparatus, the lower mold 2is lifted so that the die 1 is brought into a press contact with the thelower mold 2, whereby the top portion of the plastics container ismolded. After such molding operation of the top portion of the plasticscontainer, the lower mold 2 is lowered to perform a parting operation ofthe mold. However, in this parting operation, the molten resin in thechime "A" portion expands again so that the chime ring B is pushedupward at the notch portion B1 thereof, whereby the chime ring B oftenfloats. Consequently, a top portion of the chime ring B often projectsupward beyond a predetermined position at a time when the lower mold 2is lowered to a predetermined position. As a result, when the side molds5A, 5B are closed, they interfere with the chime ring B to be jamed,while the projecting portion of the chime "A" varies in its width. Whensuch problem occurs one step of process is required in the partingoperation of the lower mold 2 so that much more time is required in themolding operation of the plastics container, whereby it is difficult toautomate such molding operation.

The above problem can be resolved by constituting the ring portion ofthe outer side of the concave portion of the lower mold as a separatesplit mold and also by providing a suitable connecting means forselectively connecting such split mold to the lower mold between suchsplit mold and the lower mold.

By employing the above molding apparatus of the present invention, it ispossible to prevent the split mold from foating through the suitableconnecting means which connects the split mold to the lower mold in theparting operation of the lower mold. Consequently, it is also possibleto prevent the side molds from interfering with the split mold so thatthey are prevented from being jamed, while fins are prevented from beingproduced in an upper edge portion of the chime. As a result, it ispossible to reduce one step of process in the parting operationpreformed by the conventional molding apparatus, whereby it is possibleto reduce a necessary time of the molding operation of the plasticscontainer, while such molding operation can be automated.

In the embodiment of the molding apparatus of the present invention, itis preferable to construct such suitable connecting means from: a ringfixed to the lower mold and surrouding the split mold; andelectromagnetic holder embedded in the ring through a suitablenon-magnetic material member; and a rectifier or a switch forselectively supplying DC electric power to the holder.

Further, it is also possible to employ a mechanical connecting means inplace of the above magnetic connecting means. In this case, it ispreferable to employ a pin projected by a cylinder-piston unit as suchmechanical connecting means.

These connecting means will be described with reference to FIGS. 10 and11, hereinbelow.

In FIG. 10, portions corresponding to those of FIGS. 1, 2 and 5 aredesignated with the same reference numerals as those employed inn FIGS.1, 2 and 5, so that such corresponding portions will not be describedhereinbelow to avoid repeating the descriptions of such correspondingportions.

As shown in FIG. 10, on an upper surface of the lower mold 2, there ismounted a chime ring B which is a separate split mold with respect tothe lower mold 2, which chime ring B is provided with a notch portion B1corresponding to the projecting portion A1 of the chime "A" shown inFIG. 5. A ring 10 surrounding the chime ring B to form a slightclearance therebetween is fixed to the lower mold 2 through a suitablemeans (not shown). For example, in suitable manner of portions of acircumferential wall of the ring 10, there are embedded suitable numberof magnetic holders 12 through suitable non-magnetic material memberssuch as brass frames 11. The magnetic holders 12 are connected to arectifier 14 through lead wires 13 so that the electric power isselectively supplied to the magnetic holders 12 by intermittentlysupplying the current to the rectifier 14, whereby the magnetic holders12 are intermittently excited.

Now, the molding operation of the plastics container which is providedwith the chime in its top portion, and which operation is conducted withthe use of the above-mentioned mold of the present invention will bedescribed hereinbelow.

The lower mold 2 is lifted by the lift cylinder 3 to a position near thedie 1 so that a predetermined clearance is formed between the lower mold2 and the die 1, which clearance is adjusted according to a necessaryamount of the resin. In this condition, necessary amount of the resin ismeasured by means of, for example such as a timer, so that a moltenresin is extruded from the die 1.

Then, after the resin is measured, the lower mold 2 is lifted again bythe lift cyinder 3 so that the lower mold 2 is brought into a presscontact with the die 1 to mold the top portion of the plasticscontainer, which top portion is provided with the chime "A" as shown inFIG. 2.

Then, the rectifier 14 is turned so that the current is supplied to themagnetic holders 12 to excite the sames, whereby the chime ring B isconnected to the lower mold 2 through the ring 10, and the molten resinreceived in an accumulator is extruded from the die 1 by means of a ringpiston while a small amount of air is injected into the parison toprevent the parison from being in a vacuum condition. At this time, thelower mold 2 is lowered by the lift cylinder 3 at a speed according to aparison speed so that the parison P provided with a chime 4a in itslower end is formed in an expanded condition. At this time, the moltenresin in the chime "A" portion expands again so that the the chime ringB is pushed upward in its notch portion B1 in the parting operation ofthe lower mold 2. However, since the the chime B is connected to thelower mold 2 through the magnetic holders 12 and the ring 10, the chimering B is prevented from floating. When the lower mold 2 is lowered to apredetermined position, the opposite side molds 5A, 5b are closed, andthen the pressurized air is injected into the parison to perform theblow-molding operation of the plastics container. When the blow-moldingoperation the containr is finished, the rectifier 14 is turned off sothat the supplying of the current to the magnetic holders 12 is stoppedto disconnect the chime ring B from the lower mold 2, whereby the lowermold 2 is lowered by the lift cylinder 3 to be separated from the moldedcontainer. Finally, the side molds 4A, 4B are opened, and the chime ringB is split to be separated form the molded container, so that theplastics container provided with the chime "A" in its top portion isobtained.

In FIG. 11, there is shown another embodiment of the connecting meansfor connecting the chime ring B to the lowe mold 2, in which anotherembodiment the chime ring B is mechanically connected to the lower mold2 not magnetically. In such another embodiment, on suitable number ofportions of circumferential wall of the ring 10, there are mountedcylinders 20 which is provided with feeding/discharging pipes 22, 23 ofthe fluid such as oil, air and the like for actuating a piston 21. A pin24 fixed to the piston 21 is so constructed that the pin 24 can extendradially inwardly through a hole 25 provided in the ring 10 and anotherhole 26 provided in the chime ring B. Consequently, when the fluid issupplied to the cylinder 20 from the pipe 23, the pin 24 is radially andinwardly porjected so that the pin is inserted into the hole 26, wherebythe chime ring B is connected to the lower mold 2. When the fluid issupplied to the cylinder 20 from the pipe 22, the pin is retracted fromthe hole 26 so that the chime ring B is disconnected from the lower mold2.

In the above molding apparatus of the present invention, since thering-like portion of the outerside of the concave portion of the lowermold 2 is formed into a separate split-type mold and a suitableconnecting menas for connecting such slit-type mold to the lower mold 2selectively is provided therebetween, it is possible to prevent thesplit mold from floating apart from the lower mold 2 at a time of theparting operation of the lower mold 2 so that the slit mold is preventedfrom interfering with the side molds, whereby the side molds areprevented from being jamed and fins are prevented from being produced inthe upper edge portion of the chime. As a result, it is possible toreduce one step of process in the parting operation the mold relative tothe case where the conventional molding apparatus is employed, so thatthe necessary time cycle time of the molding operation is also reducedand such molding opertion can be automated.

However, in the above-mentioned blow-molding apparatus, there is aproblem in that a V-shaped notch N is apt to be produced as shown inFIG. 15D so that the molded product is decreased in its drop impactstrength and is apt to be easily exfoliated.

In order to resolve this problem, hitherto the configureation of thepinch-off portion of the mold and the molding conditions, particularlythe clamping speed of the mold are modified, for example, as to theclamping speed of the mold it is decreased, whereby the V-shaped N inthe pinch-off portion is improved to the extent of a notch configurationshown in FIG. 15E. However, such improvement is not sufficient, and evenimpairs the operativity of the molding apparatus due to the reduction ofthe clamping speed of the mold. The inventor of the present inventionhas been found that the cooling speed of the parison causes the aboveproblem, so that the problem is resolved by provisions of passages forfeeding the cooling air to each of the split-type molds in theirpinch-off portions and by provisions of passages for sucking the airreceived in the mold and by provisions of porous members in openingportions of theses passages in embedding manner.

By employing the above construction, it is possible to form a thin wallof the parison by cooling a contacting portion of the parison with ametal portion of the pinch-off portion of the mold under the effect of acooling air injected into the mold from the passages which are providedin the pinch-off portion. The air injected into the mold is then suckedso that the contacting portion of the parison to the metal of thepinch-off portion is brought into a close contact with the mold, wherebythe V-shaped notch N is prevented from being produced and a paddingoperation also can be conducted. As a result, the molded product isimproved in its drop impact strength and in its exfoliating resistance.

In the embodiment of the molding apparatus of the present invention, theabove-mentioned porous members are preferably made of sintered metal, sothat it is possible to conduct the injection action of the cooling airand the sucking action of the air received in the mold without anytrouble, and also possible to prevent the parison from entering thepassages.

Hereinbelow, actions and effects of: the passages for injecting thecooling air and the passages for sucking the air received in the moldand the porous members embedded in the opening portions of thesepassages will be described with reference to FIGS. 12 to 14. The moldingapparatus shown in FIGS. 12 to 14 is different from that shown in FIGS.1 to 11 in that the lower mold is integrated into the side molds to forma pair of opposite split-type molds in the molding apparatus shown inFIGS. 12 to 14.

As shown in FIGS. 12 and 13, a blow nozzle 202 is provided in a centralportion of the die 201 in projecting manner, which die 201 extrudes amolten resin. In a downstream side of the dies 201, there are provided apair of opposite split-type molds 203a and 203b which are clamped by thetransfer cylinders (not shown). The reference numeral 204 designates acooling water hole provided in these molds 203a, 203b in which there arealso provided suitable number of air discharging holes. Incidentally,inner surfaces of the molds 203a, 203b are coated with fluorinecontained resin. A pinch-off portion of each of these molds 203a, 203bis provided with a passage 205a or 205b (hereinafter referred to as thepassage 205), which passage 205 communicates with the outside, and in anopening portion of which passage 205 is embedded a plug 206 made ofsintered metal which is a porous member. The passage 205 is selectivelyconnected with a cooling air source A' (not shown) or a sucking vacuumsource B' (not shown) through a connector 207.

Now, the molding operation of the plastics container conducted by theblow-molding apparatus described above will be described.

A molten resin (Hizex 8200B. MFR 0.03 g/10 min. density of 0.956 g/ml)is extruded from the die 1 (a cylinder temperature: 190° C.; a dietemperature: 200° C.). The molten resin extruded from the die 1 formsthe parison P' which is received by the split-type molds 203a, 203b asshown in FIG. 13.

At a time when a front end of the parison P' reaches a downstream sidesufficiently lower than the the lowermost ends 203a', 203b' of the molds203a, 203b, the molds 203a, 203b are closed so that an upper end lowerends of the molds 203a, 203b are shut as shown in FIG. 14. Immediatelybefore completion of the clamping operation of the molds 203a, 203b, ablow-operation of the air under a pressure of, for example, 6 Kg/cm² isconducted by means of a blow nozzle 202, while a cooling air is injectedinto the mold from the passage 205 so that a mold portion for moldingthe pinch-off portion of the parison P' is cooled, whereby a surface ofthe parison P' is cooled to the extent that a thin film is formed on thesurface of the parison P'. Then, the feeding of the cooling air isstopped in dependence on a timing of the blow-operation of air, so thatthe parison P' is brought into a close contact with the inner surfacesof the molds 203a, 203b in the blow-operation of air, while the airreceived in the mold is sucked by vacuum through the passage 205,whereby the pinch-off forming portion of the parison P' is brought intoa close contact with the pinch-off portion of the mold and is formedinto a configuration provided with a thick wall porion having noV-shaped notch. At a time when the cooling action of the cooling air isconducted, if the amount of the air supplied from the right passage 205bis not sufficient, a left side of the pinch-off forming portion of themolded product is more cooled so that the thick wall portion is biasedon the left side of the molded product. In contrast with this case, thethick wall portion is biased to the right side of the molded product.Consequently, it is necessary to conduct the cooling operationuniformly. Further, since the air outside the parison P' is dischargedfrom the mold through the small air discharging holes described above,the side portion of the parison P' is brought into a close contact withboth of the molds 203a, 203b. Incidentally, at a time when the airreceived in the mold is sucked, the parison P' is prevented from beingsucked into the passage 205 by means of the plug 206, so that thesurface of the molded product is smoothly finished.

As described above, under the effect of the cooling air issued from thepassage provided in the mold in the blow-operation, the pinch-offforming portion of the parison P' can be cooled so that the V-shapednotch is eliminated from the molded product and the thick wall portionis formed in the molded product, whereby the drop impact strength of themolded product is improved.

The plastics container molded by the above molding method and the abovemolding apparatus is characterized in that the plastics container isprovided with a so-called chime in its top portion, which chime has apredetermined configuration and predetermined width and height.

However, when the plastics container is increased in size, many problemsoccur in its shipping, handling and storing. These problems are resolvedby providing a plastics container cmprising: an annular projectionformed in an outer periphery of a chime thereof; suitable number ofring-like bands which are formed in an outer periphery of a trunkportion of the plastics container and have a diameter substantiallysimilar to an outer diameter of the annular projection; a ground platewhich has a curved portion in its outer periphery and has a bottomsurface which is formed into a size adapted to an inner diameter of thechime by means of the curved portion; and a cross-like rib which has apinch-off portion and is formed inside the ground plate in projectingmanner.

It is possible to mold such plastics container by the molding method andapparatus of the present invention described above. Further, the annularprojection of the chime facilitates the use of the drum handlingmachine. Further, since it is possible to reduce a contact area of theplastics container by means of the annular projection and the ring-likeband when the plastics container falls on the ground with respect to theground, the plastic container can be easily changed in its direction intransferring operation thereof in a falling condition. Further, it ispossible to stack the plastics containers easily by inserting the bottomsurface of the ground plate of the plastics container into the innerdiameter portion of the chime of another plastic container. Further, itis possible to increase a rigidity of the bottom surface of the groundplate of the plastics container by means of the cross-like rib. As aresult, it is possible to effectively an easily transfer, stack andstore the plastics containers of the present invention.

It is preferable to make the chime and a ceiling plate of the containerthicker than the trunk portion of the same, so that it is possible toincrease the impact strength of the corners of the top portion of thecontainer. Further, it is preferable to provide a through-hole betweenthe chime and the ceiling plate so that it is possible to dischargewater stored in the ceiling plate.

Such plastics container of the present invention will be hereinbelowdescribed with reference to the drawings.

As shown in FIGS. 16a and 16b, the plastics container, i.e., a drum ofthe present invention is substantially constructed of: a trunk portion301; a ceiling plate 302 covering an upper opening of the trunk portion301; a ground plate 303 covering a lower opening of the trunk portion301; and a chime 304 which is provided in an upper portion of an outerperiphery of the ceiling plate 302 in projecting manner and is equal inits outer diameter to that of the trunk portion 301. The ceiling plate302 and the chime 302 are made thicker than the trunk portion 301. Athrough-hole 305 which communicates with the outside is provided betweenthe chime 304 and the ceiling plate 301. Incidentally, the referencenumeral 306 designates a tap; the numeral 307 designates a pinch-offportion which is laterally formed in the groun plate 303 in a straightline manner.

An annular projection 308 is formed in an outer periphery of an upperedge portion of the chime 304. In suitable positions of an outerperiphery of the trunk portion 301 there are formed suitable number ofring-like bands 309 (in the embodiment shown, the number of thering-like bands is two), an outer diameter of which ring-like band 309is equal to that of the annular projection 308. Further, if necessary,there are provided suitable number of ribs R' in the projection 308.

In an outer periphery of the ground plate 303, there is formed a curvedportion 310 leading to the trunk portion 301. By means of such curvedportin 310, a bottom surface or a ground plate surface 311 of the grounplate 303 is formed into a size adapted to an inner diameter of thechime 304, in which ground plate surface 311 there is formed a pinch-offportion 307 which is included in a cross-like rib 312 formed inside theground plate 303 in projecting manner. Since the plastics container ofthe present invention has the above construction, the use of the drumhandling machine is faciltated by means of the projection 308 of thechime 304. Further, since it is possible to reduce a ground contactingarea of the plastics container by emans of the annular projection 308and the ring-like bands 309 when the plastics container falls on theground, the plastics container can be easily changed in its movingdirection in transferring operation thereof in a falling condition.Further, it is possible to stack the plastics containers easily byinserting the ground plate surface 311 into the inner diameter portionof the chime 304. Further, it is possible to increase a rigidity of theground plate surface 311 by means of the rib 312. Further, it ispossible to make the ceiling plate 302 and the chime 308 thicker toincrease the impact strength of the corners of the top portion of theplastics container. Further, it is possible to discharge water stored inthe ceiling plate 302 through the through-hole 305.

In the embodiment of the plastics container which is provided with thechime in its top portion and is molded by the blow-molding operationaccording to the present invention, since the plastics containercomprises: the annular projection 308 formed in the outer periphery ofthe chime 304 thereof; suitable number of the ring-like bands 309 whichare formed in the outer periphery of the trunk portion 301 of theplastics container and have the diameter substantially similar to theouter diameter of the annular projection 308; the ground plate 303 whichhas the curved portion 310 in its outer periphery and has the bottomsurface or the ground plate surface 311 which is formed into the sizeadapted to the inner diameter portion of the chime 304 by means of thecurved portion 310; and the cross-like rib 312 which has the pinchoffportion 307 and is formed inside the ground plate 303 in projectingmanner, it is possible to facilitate the use of the drum handlingmachine, and to easily change the container in its moving direction, andto stack the containers easily, and to increase the rigidity of theground plate surface of the container. As a result, it is possible toefficiently and easily transfer, stack and store the plasticscontainers.

What is claimed is:
 1. A plastics container molded by a blow-moldingoperation and provided with a chime in its top-portion, comprising:anannular projection formed in an outer periphery of said chime; suitablenumber of ring-like bands formed in an outer circumferential surface ofa trunk portion of said plastics container, said ring-like band being inits outer diameter similar to that of said annular projection of saidchime; a ground plate provided with a curved surface portion in itsouter periphery and having its bottom surface adapted to an innerdiameter of said chime by means of said curved surface portion; and across-like rib containing a pinch-off portion therein and providedinside said ground plate in projecting manner.